In an information recording medium, such as a CD and a DVD, for example, as described in patent documents 1 and 2, etc., there is also developed an information recording medium, such as a multilayer type or dual layer type optical disc, in which a plurality of recording layers are stacked or bonded on the same substrate. Then, on an information recording apparatus, such as a DVD recorder, for performing the recording with respect to the dual layer type, i.e., two-layer type optical disc, laser light for recording is focused on a recording layer located on the front as viewed from the irradiation side of the laser light (hereinafter referred to as an “L0 layer”, as occasion demands) to thereby record information into the L0 layer in an irreversible change recording method by heat or a rewritable method. Moreover, the laser light is focused on a recording layer located on the rear of the L0 layer as viewed from the irradiation side of the laser light (hereinafter referred to as an “L1 layer”, as occasion demands), through the L0 layer or the like, to thereby record information into the L1 layer.
On the other hand, there is also disclosed a technology of performing the recording or reproduction in an “opposite method” or the like with respect to the L0 layer and the L1 layer. The “opposite method” herein is a recording or reproducing method in which track path directions are opposite between two recording layers, for example.
In the two-layer type optical disc adopting this opposite method, as described in a patent document 3, it is necessary to record a middle area, as a buffer area, in disc outer circumferential portions of the L0 layer and the L1 layer. This middle area plays the same role as a lead-out in the case of single-layer type media, and it is a buffer area for preventing an unrecorded area from being adjacently located just behind an information recorded-area.
In the same manner, as the buffer area, a border zone is recorded in some cases, in an optical disc of DVD-R/RW or the like, for example. The border zone herein is a buffer area for preventing an unrecorded area from being adjacently located just behind an area where information, such as data, is recorded, as in the case of the lead-out and the middle area. More specifically, the border zone has a structure prepared for a write-once method, such as multi session in a CD-R, even in a DVD-R. Incidentally, the recording process of the border zone is generally referred to as border close (process).
By recording such a buffer area to eliminate, in the DVD-R or the like, the unrecorded area adjacent to the data, it is possible to perform the normal control of tracking servo, by an optical pickup of a DVD-ROM reproduce-only drive which adopts a phase difference method or differential phase detection, with respect to a DVD-R drive which adopts a push-pull method as a tracking method.
As described above, by virtue of the presence of the middle area and the border zone, the DVD-ROM reproduce-only drive can accurately read the information on the optical disc of DVD-R/RW or the like, whose compatibility with the DVD -ROM is maintained.    Patent document 1: Japanese Patent Application Laying Open NO. 2000-311346    Patent document 2: Japanese Patent Application Laying Open NO. 2001-23237    Patent document 3: Japanese Patent Application Laying Open NO. 2000-503446    Patent document 4: Japanese Patent Application Laying Open NO. 2002-133667    Patent document 5: Japanese Patent Application Laying Open NO. 2003-59059    Patent document 6: Japanese Patent Application Laying Open NO. Hei 09-16966    Patent document 7: Japanese Patent Application Laying Open NO. 2001-23237